The RAF crew decided that the supplies could have injured some of the thousands of people who are gathered on Mount Sinjar in Iraq's north, desperate to escape the IS onslaught with the radical jihadist having already massacred around 500 Yezidis.

It comes as one of Britain's most senior generals accused the "commitment-phobic" Government of being "terrified" of intervening in the Iraq crisis before next year's general election. General Sir Richard Shirreff told the Times "the longer we sit on our hands and prevaricate, the more dangerous the situation is going to become".

A displaced Iraqi man from the Yazidi community carries his daughter as they cross the Iraqi-Syrian border at the Fishkhabur crossing, in northern Iraq

“If you are going to do anything, if you are serious about avoiding a humanitarian disaster, you have got to do it properly. These things don’t go away. We have got a situation. There is no way round it. You have just got to go through it and resolve it.”

Foreign Secretary Philip Hammond, who chaired a meeting of the Government's emergency Cobra committee to discuss the crisis, said the situation was "challenging" and warned of a "potential humanitarian disaster on a huge scale". Hammond has rejected calls for Parliament to be recalled to discuss the crisis and said there were no plans for British military involvement. "We don't envisage a combat role at the present time," he said.

Downing Street also confirmed the RAF would send "a small number" of Tornado jets to the region so they can be used, if required, to improve the UK's surveillance capability in the region to help the humanitarian effort. The UK will also look at how it can play a role in getting equipment to Kurdish forces as they are better able to counter IS, formerly known as ISIS Number 10 added.

Barack Obama said the US had "stepped up" its support to Iraqi and Kurdish forces engaged in the fight on the ground and was continuing with its daily humanitarian efforts. The president said: "I want to thank in particular the UK, France and other countries working with us to provide much needed assistance to the Iraqi people."

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UK Aid Drop For Iraq

UK Aid Drop For Iraq

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The next air drop of humanitarian aid in northern Iraq is likely to be carried out within the next 24 hours after RAF crews were forced to abandon their attempt to deliver supplies the previous night. The UK has already made one successful aid flight, dropping supplies including water and solar lanterns, to Mount Sinjar, where members of the of Yazidi minority are trapped in extreme conditions after fleeing the advance of the IS forces.

David Cameron, who is on holiday in Portugal, has been urged to call MPs back from their summer break to discuss the crisis and he has also faced pressure - including from former head of the Army Lord Dannatt - to consider a military intervention.

President Fouad Massoum's decision could trigger further infighting in the country, which is already struggling to cope with the IS insurgency.

Speaking from his rented holiday home on Martha's Vineyard, Massachusetts, Obama called the appointment of new prime minister al-Ibadi a "promising step forward". He said he had called to congratulate him and urge him to form a new and inclusive cabinet as quickly as possible.

"Meanwhile I urge all Iraqi political leaders to work peacefully through the political process in the days ahead," Obama said.